This invention relates to formulations useful as lubricants for polyethylene snow sliders such as skis, snowboards and sleds. Lubricants of this type are of particular interest as ski waxes since they reduce friction between the polyethylene running surface of the ski and the snow, which results in higher skiing speeds.
A ski in motion possesses kinetic energy and the more of this energy it maintains, the faster it will move. Some of this energy is lost through friction and is converted to heat or is lost due to the vibration of the ski. Energy is also expended for plowing and compaction which occur when the snow is compressed or pushed aside as the ski is moving. The less energy a moving ski consumes through plowing and compaction, vibration and friction, the more kinetic energy--and consequently, speed--it retains.
There are several methods of minimizing kinetic energy loss. For example, to minimize kinetic energy loss due to plowing and compaction a race course is compacted mechanically prior to the race. Vibration, which is characteristic of the ski, is reduced by the proper utilization of ski construction materials.
Kinetic energy loss due to friction can also be minimized. The following friction components may be present in a glide situation:
1. Dry friction, which occurs in areas where dry snow particles touch the ski base; PA1 2. Capillary suction, which occurs when free water is present and adheres to the base, producing a suction effect; PA1 3. Friction due to the presence of dirt (i.e., diesel oil, pollen, rock-dust), which occurs when atmospheric contaminants adhere to the base and the snow at the same time, connecting them and reducing speed. PA1 4. Friction due to static electricity, which is generated triboelectrically when the base slides on snow and increases the friction between the polyethylene (as well as the steel ski edges) and the snow. PA1 A. Base structuring: Various textures are imprinted on the polyethylene ski bases by the manufacturers. Their purpose is to reduce capillary suction by preventing the formation of continuous water films and minimize the contact area between the base and the snow. PA1 B. Inclusion of antistatic materials in the base: Up to 15% of graphite and carbon black are added to the polyethylene base materials to enhance its antistatic properties. PA1 C. Waxing: Ski waxes are solid lubricants that reduce friction between the ski and the snow. When selecting a wax, one optimizes the following five properties: PA1 1. Hardness--The wax must always be harder than the snow so the snow does not penetrate it. PA1 2. Friction coefficient--The friction coefficient must be as low as possible. PA1 3. Water repellency--Water repellency must be as high as possible to overcome capillary suction. PA1 4. Dirt absorption--The wax must not absorb dirt, pollen or oily atmospheric contaminants. PA1 5. Antistatic properties--The wax must not generate static electricity when rubbed. PA1 They generate static electricity when rubbed which attracts dirt and impairs glide. PA1 They exhibit only moderate water repellency, so water capillary suction often reduces speed. PA1 R.sub.f CH.sub.2 CH.sub.2 SH+CH.sub.2 =CH(CH.sub.2).sub.m-2 CH.sub.3 +radical initiator.fwdarw.R.sub.f CH2CH.sub.2 S(CH.sub.2).sub.m CH.sub.3 R.sub.f CH2CH.sub.2 S(CH.sub.2).sub.m CH.sub.3 +oxidizing agent.fwdarw.R.sub.f CH2CH.sub.2 SO.sub.2 (CH.sub.2).sub.m CH.sub.3 PA1 R.sub.f SO.sub.2 CI+RNH(CH.sub.2).sub.m CH.sub.3 .fwdarw.R.sub.f SO.sub.2 NR(CH.sub.2).sub.m CH.sub.3
Three main methods have been used to reduce kinetic energy loss due to friction:
Paraffins, microcrystalline waxes and synthetic (polyethylene or Fischer-Tropsch) waxes are typically used for ski wax formulation. Almost all ski waxes formulated for warm snow conditions are blends of soft paraffins and soft microcrystalline waxes. Blends of harder paraffins and microcrystalline waxes are used for more aggressive snow. Synthetic waxes are very effective wax blend hardeners so they are frequently added to wax formulations intended for use on very cold snow. The above hydrocarbon ski waxes have two disadvantages:
Graphite is often added to hydrocarbon waxes in amounts ranging from one to five percent by weight to impart antistatic properties and reduce dirt absorption. The generally accepted explanation is that graphite, being conductive, eliminates static electricity. Unfortunately, graphite also increases the internal friction of the wax which in turn reduces gliding speed. Graphite also reduces the hydrophobicity of paraffins which in turn impairs performance on wet snow. Therefore, the usefulness of graphite containing waxes is limited to racing on cold, dry snow and to long distance racing on very dirty snow where dirt absorption would significantly reduce speed.
Hydrocarbon-wax-miscible or dispersible fluorinated additives have been developed to improve the water repellency of hydrocarbon waxes. European Patent Application 0 421 303 A2 describes hydrocarbon wax miscible fluoroesters and polyfluoroalkyl ester copolymers for use as lubricants for skis; International Application WO 94/11468 describes hydrocarbon wax miscible perfluoroalkyl terminated urethane lubricants; U.S. Pat. No. 5,423,994 describes hydrocarbon wax miscible substituted alkanes of the formula C.sub.n H.sub.2n+1 C.sub.m F.sub.2m+1. All of the aforementioned additives, however, are believed to increase static electricity build-up and, furthermore, are not suitable for snow temperatures below -10.degree. C. FR 2637907 describes dispersions of a blend of carbon fluorides (CF.sub.x).sub.n in hydrocarbon wax. Although the carbon fluorides improve acceleration on colder snow, performance on wet snow is modest.